Modified asphalt binders and asphalt paving compositions

ABSTRACT

A modified asphalt binder composition prepared by combining asphalt binder, phosphorus pentasulfide, and less than 2.5 parts by weight unsaturated polymer, per 100 parts by weight asphalt binder, to thereby produce a modified asphalt binder composition characterized by an elongation recovery at 25° C., as determined according to AASHTO T301, of greater than 75%.

This application is a continuation of U.S. application Ser. No.12/628,667, filed Dec. 1, 2009, now U.S. Pat. No. 7,816,429 which is acontinuation of U.S. application Ser. No. 11/644,557, filed Dec. 22,2006, now U.S. Pat. No. 7,781,503 which claims the benefit of U.S.Provisional Application Nos. 60/755,666, 60/755,670, 60/755,668,60/755,667, filed Dec. 29, 2005, and U.S. Provisional Application No.60/813,950, filed Jun. 15, 2006, all of which are incorporated herein byreference.

FIELD OF THE INVENTION

One or more embodiments of the present invention are directed towardmodified asphalt binder compositions that are prepared by employingphosphorus pentasulfide and polymer, as well as asphalt pavingcompositions prepared using these binder compositions.

BACKGROUND OF THE INVENTION

Asphalt paving compositions, which include a mixture of asphalt binderand aggregate, have long been employed in the manufacture of pavements.The long-standing technological challenge with these pavements has beentheir behavior at extreme temperatures. That is, at high temperatures,the pavements become soft; and at low temperatures, the pavements arebrittle.

For decades, additives have been employed to alleviate the problemsexperienced at extreme temperatures. For example, polymers have beenadded to asphalt binder compositions. U.S. Pat. No. 4,145,322 teachespolymer-modified bitumen compositions that include elastomers (e.g.,polyisoprene, butyl rubber, SBR rubber) that can be employed to improvethe mechanical properties of the bitumens, especially the elastomericproperties. And, the use of particular block copolymers of styrene anddiene monomer in these bitumen compositions provides compositions havingdesirable mechanical properties even at low temperatures.

In a similar fashion, JP 51-149312 (1976) teaches modified asphaltcompositions that include a phosphorus compound, such as phosphoruspentoxide, polyphosphoric acid, or phosphorus pentasulfide. It issuggested that these phosphorus compounds can modify the asphalt becausethey bond to the asphaltene in the asphalt to further strengthen the gelstructure. In order to overcome dispersibility and handling issuesassociated with these phosphorus compounds, the phosphorus compounds aremixed with petroleum compositions, and the mixture is added to theasphalt composition. The petroleum compositions are characterized by anignition point of 150° C. or higher and include 0.5-40% asphaltenes. Thephosphorus compounds can be included in the petroleum composition in anamount from 0.5 to 50 weight percent, and the amount of phosphoruscompound added to the asphalt to be modified may be from 0.2 to 5.0weight percent.

U.S. Pat. No. 6,569,351 teaches polymer modified asphalt compositionsprepared by combining an accelerator-gel additive with polymer andasphalt, and curing the polymer-modified asphalt at a temperaturebetween 200° F. and 500° F. The accelerator-gel additives include 2-75%accelerator, 25-88% processing oil, and 0.5-10% clay. The acceleratormay include sulfur, 4,4′-dithiodimorpholine, thiazole derivatives,dithiocarbanates, phosphorus pentasulfide, phosphorus pentoxide, zincstearate, ammonium stearate, sodium hydroxide, potassium hydroxide,calcium hydroxide, aluminum oxide, or combinations of these or othervulcanizers or accelerators. The accelerator-gel additive may be addedto concentrates between approximately 1-25% polymer.

U.S. Pat. No. 5,990,206 teaches a mixture of polymer and phosphoruscompound (modifier composition) for use in asphalt compositions. Thepolymer may include a rubber-base polymers (modifier) and/or aresin-based polymer (modifier). The phosphorus compounds may includephosphoric anhydride (P₂O₅), polyphosphoric acid, orthophosphoric acid,phosphorus oxytrichloride (POCl₃), phosphorus trichloride (PCl₃), andphosphorus pentasulfide (P₂S₅). The mixture may contain from about 0.1to about 10% by weight of the phosphorus compound, and asphaltcompositions containing from 0.1 to 30% by weight of thepolymer/phosphorus compound blend (modifier composition) may beprepared. It is believed that the inorganic phosphorus compoundfunctions as a crosslinking agent between the rubber-base and/orresin-base modifier, and a higher order network structure (asphaltene)in the asphalt, and is useful to strengthen the gel structure in theasphalt.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a flow chart showing a particular embodiment of thepresent invention.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a process forpreparing a modified asphalt binder composition, the process comprisingmixing asphalt, an unsaturated polymer, and phosphorus pentasulfide toform a modified asphalt composition.

One or more embodiments of the present invention also provide a processfor preparing a modified asphalt binder composition, the processcomprising mixing asphalt binder, polymer, and phosphorus pentasulfideto form a modified asphalt composition, where the weight ratio ofpolymer to phosphorus pentasulfide is at least 0.5:1 and less than 8:1.

One or more embodiments of the present invention further provide aprocess for preparing a modified asphalt binder composition the processcomprising introducing an polymer to an asphalt binder, and introducingphosphorus pentasulphide to an asphalt binder, where said step ofintroducing phosphorus pentasulfide to the asphalt includes adding aphosphorus pentasulfide composition that includes less 5% by weighthydrocarbon material.

One or more embodiments of the present invention still further provide amethod for forming a modified asphalt binder composition, the methodcomprising preparing a phosphorus pentasulfide-binder concentrate byintroducing and mixing phosphorus pentasulfide and asphalt binder, wherethe phosphorus pentasulfide-binder concentrate includes greater than 0.5parts by weight phosphorus pentasulfide per 100 parts by weight asphalt,preparing a polymer-binder concentrate by introducing and mixing polymerand asphalt binder, where the polymer-binder concentrate includesgreater than 5 parts by weight polymer per 100 parts by weight asphalt,and introducing and mixing the phosphorus pentasulfide-binderconcentrate with the polymer-binder concentrate to form a modifiedasphalt binder composition.

One or more embodiments of the present invention also provide a modifiedasphalt binder composition comprising the combination or the reactionproduct of an asphalt, phosphorus pentasulfide, and an unsaturatedpolymer.

One or more embodiments of the present invention also provide a modifiedasphalt binder composition prepared by a process comprising introducingand mixing an asphalt, phosphorus pentasulfide, and polymer, where theweight ratio of the polymer to the phosphorus pentasulfide is at least0.5:1 and less than 8:1.

One or more embodiments of the present invention further provide anasphalt composition which comprises the reaction product of an asphalt,an unsaturated polymer, a source of phosphorus and a source of sulfur,wherein the source of phosphorus and the source of sulfur form reactivecrosslinks between components of the asphalt and the unsaturatedpolymer.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

One or more embodiments of the present invention provide a method forforming a modified asphalt binder composition that is useful forpreparing asphalt paving compositions. In one or more embodiments, themodified asphalt binder composition may be formed by introducing andmixing an asphalt binder, a polymer, and phosphorus pentasulfide. Themodified asphalt binder composition may be combined with aggregate toform an asphalt paving composition. In particular embodiments, theasphalt paving composition can be formed into pavements.

The term “asphalt binder” is used as understood by those skilled in theart and is consistent with the meaning provided by AASHTO M320. Whereasphalt binder has been combined with aggregate, the term “asphaltpaving composition” is employed. As used within this specification, theterms “asphalt” and “asphalt binder” may be used synonymously. Theasphalt binder material may be derived from any asphalt source, such asnatural asphalt, rock asphalt, produced from tar sands, or petroleumasphalt obtained in the process of refining petroleum. The asphaltbinder may be selected from those currently graded by AASHTO M320 andASTM D-6373, including Performance Graded Asphalt Binders. In otherembodiments, asphalt binders may include a blend of various asphalts notmeeting any specific grade definition. This includes air-blown asphalt,vacuum-distilled asphalt, steam-distilled asphalt, cutback asphalt orroofing asphalt. Alternatively, gilsonite, natural or synthetic, usedalone or mixed with petroleum asphalt, may be selected. Syntheticasphalt mixtures suitable for use in the present invention aredescribed, for example, in U.S. Pat. No. 4,437,896. In one or moreembodiments, asphalt includes petroleum derived asphalt and asphalticresidual. These compositions may include asphaltenes, resins, cyclics,and saturates. The percentage of these constituents in the overallasphalt binder composition may vary based on the source of the asphalt.

Asphaltenes include black amorphous solids containing, in addition tocarbon and hydrogen, some nitrogen, sulfur, and oxygen. Trace elementssuch as nickel and vanadium may also be present. Asphaltenes aregenerally considered as highly polar aromatic materials of a numberaverage molecular weight of about 2000 to about 5000 g/mol, and mayconstitute about 5 to about 25% of the weight of asphalt.

Resins (polar aromatics) include dark-colored, solid and semi-solid,very adhesive fractions of relatively high molecular weight present inthe maltenes. They may include the dispersing agents of peptizers forthe asphaltenes, and the proportion of resins to asphaltenes governs, toa degree, the sol- or gel-type character of asphalts. Resins separatedfrom bitumens may have a number average molecular weight of about 0.8 toabout 2 kg/mol but there is a wide molecular distribution. Thiscomponent may constitute about 15 to about 25% of the weight ofasphalts.

Cyclics (naphthene aromatics) include the compounds of lowest molecularweight in bitumens and represent the major portion of the dispersionmedium for the peptized asphaltenes. They may constitute about 45 toabout 60% by weight of the total asphalt binder, and may be dark viscousliquids. They may include compounds with aromatic and naphthenicaromatic nuclei with side chain constituents and may have molecularweights of 0.5 to about 9 kg/mol.

Saturates include predominantly the straight- and branched-chainaliphatic hydrocarbons present in bitumens, together with alkylnaphthenes and some alkyl aromatics. The average molecular weight rangemay be approximately similar to that of the cyclics, and the componentsmay include the waxy and non-waxy saturates. This fraction may fromabout 5 to about 20% of the weight of asphalts.

In these or other embodiments, asphalt binders may include bitumens thatoccur in nature or may be obtained in petroleum processing. Asphalts maycontain very high molecular weight hydrocarbons called asphaltenes,which may be soluble in carbon disulfide, pyridine, aromatichydrocarbons, chlorinated hydrocarbons, and THF. Asphalts or bituminousmaterials may be solids, semi-solids or liquids.

In one or more embodiments, the asphalt binders, prior to modification(i.e., prior to combination with unsaturated polymer or P₂S₅), may becharacterized by a PG rating of at least PG 64-22, in other embodimentsat least PG 52-28, and in other embodiments at least PG 52-34. It shouldbe noted that each of these exemplary asphalt binders have a temperatureperformance range of 86° C. While the selection of these asphalt bindersmay be advantageous desirable and certain embodiments, practice of thepresent invention advantageously allows for the use of a base asphaltbinder with a lower temperature range because this lower temperaturerange can be upgraded through practice of the present invention. Forexample, a PG 64-16, PG 58-22, or PG 52-28 can be modified to increaseits temperature range. As those skilled in the art appreciate, PG ratingrefers to Super Pave (Superior Performing Pavements) Performance Graded(PG) binder specifications as developed in the United States throughresearch funded by the Association of American Highway andTransportation Officials (AASHTO M320).

In one or more embodiments, the polymers may be characterized by a glasstransition temperature (Tg), as measured by DSC analysis, of less than20° C., in other embodiments less than 0° C., in other embodiments lessthan −20° C., in other embodiments less than −35° C., and in otherembodiments from about −90° C. to about −20° C.

In one or more embodiments, the polymer employed is an unsaturatedpolymer. In one or more embodiments, unsaturated polymers includehydrocarbon-based polymers that have a degree or amount of unsaturationthat may be quantified based upon the number of double bonds (eitherbackbone or pendant non-conjugated double bonds) per total number ofcarbon atoms within a polymer (including pendant carbon atoms). Forexample, in one or more embodiments, the unsaturated polymers include atleast 5 double bonds, in other embodiments at least 7 double bonds, inother embodiments at least 12 double bonds, and in other embodiments atleast 16 double bonds per 100 carbon atoms in the polymer. In these orother embodiments, the unsaturated polymers include from about 7 toabout 25 double bonds, in other embodiments from about 10 to about 20double bonds, and in other embodiments from about 12 to about 18 doublebonds per 100 carbon atoms.

Unsaturated polymers include those polymers that include backbone,pendant, or both backbone and pendant unsaturation (i.e., non-conjugateddouble bonds). For example, mer units deriving from the1,2-polymerization mechanism of 1,3-butadiene, or mer units derivingfrom the 3,4 polymerization mechanism of isoprene, are pendant, vinylunits. The amount of pendant non-conjugated double bonds may bequantified based on the vinyl percentage of the mer units containingunsaturation. For example, a polymer having 30% vinyl content refers toa polymer in which 30% of unsaturated mer units are pendantnon-conjugated double bonds. In one or more embodiments, the unsaturatedpolymers employed in practicing the present invention include zero oronly negligible vinyl content. In other embodiments, unsaturatedpolymers include low vinyl content (e.g., 1 to about 10%); in otherembodiments, they include medium vinyl content (e.g., 11 to 40%); and inother embodiments, they include high vinyl content (e.g., greater than40%).

In one or more embodiments, the unsaturated polymers may also includemer units that do not include non-conjugated double bonds. For example,mer units deriving from the polymerization of comonomer, such asstyrene, do not include non-conjugated double bonds. In one or moreembodiments, the unsaturated polymers may include from about 0% to about55% mer units (i.e., based upon moles), in other embodiments from about3 to about 50% mer units, and in other embodiments from about 10 toabout 45% mer units deriving from monomer that does not providenon-conjugated double bonds (e.g., styrene).

In one or more embodiments, the unsaturated polymers may becharacterized by a melt index (ASTM D-1238; 2.16 kg load @ 190° C.) ofless than 1,000 dg/min, in other embodiments less than 500 dg/min, inother embodiments less than 50 dg/min, in other embodiments less than 20dg/min, in other embodiments less than 10 dg/min, and in otherembodiments less than 1 dg/min. In these or other embodiments, theunsaturated polymers may have a melt index of between 3 and 15 dg/min,and other embodiments between 4 and 12 dg/min.

In one or more embodiments, the unsaturated polymers may becharacterized by a number average molecular weight (M_(n)) of from about10 to about 1,000 kg/mol, in other embodiments from about 40 to about500 kg/mol, and in other embodiments from about 80 to about 200 kg/mol.In these or other embodiments, the unsaturated polymers may also becharacterized by a weight average molecular weight (M_(W)) of from about10 to about 4,000 kg/mol, in other embodiments from about 40 to about2,000 kg/mol, and in other embodiments from about 80 to about 800kg/mol. In one or more embodiments, the unsaturated polymers may becharacterized by a molecular weight distribution of from about 1.1 toabout 5, in other embodiments from about 1.5 to about 4.5, and in otherembodiments from about 1.8 to about 4.0. Molecular weight can bedetermined by gel permeation chromatography (GPC) calibrated withpolystyrene standards and adjusted for the Mark-Houwink constants forthe polymer in question.

The hydrocarbon based unsaturated polymers may be linear, branched, orcoupled polymers. Types of hydrocarbon polymers may include both naturaland synthetic polymers. Useful synthetic polymers may include polydienesor polydiene copolymers with non-diene comonomer (e.g., styrene). Thecopolymers may include block and random copolymers. The coupled polymersmay include linearly coupled polymers (e.g. di-coupled polymers) orraidally coupled polymers (e.g. tri-coupled or, tetra-coupledpenta-coupled, hexa-coupled etc.). Exemplary polydienes includepolybutadiene and polyisoprene. Exemplary copolymers may include randomstyrene-butadiene rubber, styrene-butadiene block copolymer,styrene-butadiene-styrene block copolymer, random styrene-isoprene,styrene-isoprene block copolymer, styrene-isoprene-butadiene blockcopolymer, random styrene-isoprene-butadiene, styrene-isoprene-styreneblock copolymer, and chloroprene rubber. In one or more embodiments, thepolymer may include a high-vinyl block copolymer as described inInternational Application No. PCT/US2005/028343. In one or moreembodiments, the unsaturated polymers include linear or radial blockcopolymers wherein the block copolymers include terminal styrene blocks.For example, in the case of a radial tri-coupled polymer, each of thethree radial arms of the polymer will include terminal styrene blocks.In these or other embodiments, the internal segments of the radial armsinclude polydiene blocks such as polybutadiene blocks. In these or otherembodiments, the styrene content of these block copolymers may be from10% to 50% by weight, in other embodiments from 15% to 45% by weight,and in other embodiments from 20% to 40% by weight.

In one or more embodiments, the polymer may include ananionically-polymerized polymer. In other embodiments, the polymer maybe produced by coordination catalysis such as by using cobalt-based,nickel-based, or lanthanide-based coordination systems.

In one or more embodiments, the polymer may include a polydiene and/orpolydiene copolymer including a polar group. These polar groups may bepositioned pendant to the polymer backbone and/or at the terminus of thepolymer backbone. In one or more embodiments, the polar group mayinclude a carbonyl group such as a carboxylic acid group or an anhydridegroup, hydroxyl group, amino group, amido group, carbamate group,silicon-containing, metal-containing groups, phosphorus-containinggroups and the like.

In one or more embodiments, the polymer may be introduced to the asphaltcompositions in several forms. For example, the polymer can be added asa crumb, as ground polymer, as pellets, as molten polymer, or as aliquid polymer.

In one or more embodiments, phosphorus pentasulfide includes thosecompounds defined by the empirical formula P₂S₅ or P₄S₁₀, both of whichare used synonymously by those skilled in the art. In one or moreembodiments, phosphorus pentasulfide compounds include those defined bythe formula

or its phosphorus-rich derivatives. These phosphorus-rich derivativesare believed to result when a sulfur atom that is doubly bonded to aphosphorus atom is lost. In one or more embodiments, the phosphorusconcentration of the phosphorus pentasulfide compositions is at least27.85 weight percent, in other embodiments from about 27.87 to about28.3 weight percent, and in other embodiments from about 28.90 to about28.00 weight percent. Phosphorus pentasulfide is commercially availablefrom sources such as ICL Performance Products, L.P.

In one or more embodiments, the phosphorus pentasulfide that is employedin the present invention is so employed in its solid form such as solidparticulate. In one embodiment, phosphorus pentasulfide may becharacterized by having a particle size (i.e. average diameter) of lessthan 20 mm, in other embodiments less than 2 mm, in other embodimentsless than 0.2 mm, and in other embodiments less than 0.02 mm; in theseor other embodiments, the particle size may be greater than 0.001 mm, inother embodiments greater than 0.009 mm, and in other embodimentsgreater than 0.01 mm. In these or other embodiments, the medium particlesize of the phosphorus pentasulfide may be from about 0.03 to about 1.00mm, in other embodiments from about 0.05 to about 0.95 mm, in otherembodiments from about 0.06 to about 0.90 mm, and in other embodimentsfrom about 0.07 to about 0.085 mm. In these or other embodiments, atleast 30%, in other embodiments at least 50%, and in other embodimentsat least 70% of the phosphorus pentasulfide particles fall within therange from about 0.03 to about 1.00 mm, and in other embodiments fromabout 0.05 to about 0.95 mm, in other embodiments from about 0.06 toabout 0.90 mm, and in other embodiments from about 0.07 to about 0.085mm.

The phosphorus pentasulfide employed in the present invention may berelatively pure. In one or more embodiments, the phosphorus pentasulfideincludes less than 10 weight percent, in other embodiments less than 5weight percent, in other embodiments less than 2 weight percent, and inother embodiments less than 0.5 weight percent impurities. Also, in oneor more embodiments, the phosphorus pentasulfide, as introduced to theasphalt for mixing therewith, is in its neat form. In one or moreembodiments, phosphorus pentasulfide in its neat form refers to solidparticulate that contains less than 5 weight percent, in otherembodiments less than 2 weight percent, in other embodiments less than0.5 weight percent, in other embodiments less than 0.1 weight percent,and in other embodiments less than 0.05 weight percent organic orhydrocarbon matter or impurities.

In one or more embodiments, the phosphorus pentasulfide may be employedwithout modification. In other embodiments, phosphorus pentasulfideincludes those materials that have not been reacted or have notundergone any reaction or pre-reaction to modify the solubility of thephosphorus pentasulfide within an asphalt composition. For example, ithas advantageously been found that phosphorus pentasulfide may beemployed without reacting it with a compound having a hydroxyl groupcapable of bonding to the phosphorus pentasulfide. In one or moreembodiments, the phosphorus pentasulfides may employed withoutpre-reacting the phosphorus pentasulfide with a polyalkylene oxide.

The modified asphalt binder compositions of this invention may alsoinclude those other ingredients or constituents that are commonlyemployed in the industry. For example, the compositions may includeanti-stripping compounds.

In other embodiments, curing agents can optionally be added to themodified asphalt binder compositions of this embodiment. Curing agentsmay include phenolic resins and elemental sulfur. One example is abismaleimide curing agent. Conventional amounts may be employed inpracticing this invention. In one or more embodiments, the need for acuring agent, particularly sulfur, is eliminated. In other words,asphalt binder compositions of the present invention can be preparedwithout the addition of a curing agent and/or a sulfur-containingcurative other than the phosphorus pentasulfide.

The asphalt binder compositions of the present invention may includefrom about 0.1 to about 10 parts by weight, in other embodiments fromabout 0.2 to about 6 parts by weight, and in other embodiments fromabout 0.5 to about 4 parts by weight polymer per 100 parts by weightasphalt binder. In these or other embodiments, the asphalt bindercompositions of the present invention may include less than 5 parts byweight, in other embodiments less than 4 parts by weight, in otherembodiments less than 3 parts by weight, in other embodiments less than2.5 parts by weight, in other embodiments less than 2 parts by weight,in other embodiments less than 1.8 parts by weight, in other embodimentsless than 1.5 parts by weight polymer per 100 parts by weight asphaltbinder. In these or other embodiments, the asphalt binder compositionsinclude at least 0.1 parts by weight, in other embodiments at least 0.5parts by weight, in other embodiments at least 0.7 parts by weight, inother embodiments at least 1.0 parts by weight, and in other embodimentsat least 1.2 parts by weight polymer per 100 parts by weight asphaltbinder.

The asphalt binder compositions of the present invention may includefrom about 0.001 to about 10, in other embodiments from about 0.05 toabout 5, and in other embodiments from about 0.01 to about 1 part byweight phosphorus pentasulfide per 100 parts by weight asphalt binder.

In one or more embodiments, the weight ratio of unsaturated polymer tophosphorus pentasulfide within the modified asphalt binder compositionmay be at least 0.5:1, in other embodiments at least 0.7:1, in otherembodiments at least 1:1, in other embodiments at lest 1.3:1, in otherembodiments at least 1.5:1, in other embodiments at least 1.8:1, and inother embodiments at least 2.0:1. In these or other embodiments, theweight ratio of unsaturated polymer to phosphorus pentasulfide is lessthan 8:1, in other embodiments less than 7:1, in other embodiments lessthan 6:1, in other embodiments less than 5:1, in other embodiments lessthan 4:1, and in other embodiments less than 3:1.

In those embodiments where a curative is employed, the asphaltcompositions of this invention may include from about 0.1 to about 10,in other embodiments from about 0.2 to about 6, and in other embodimentsfrom about 0.5 to about 4 parts by weight curative per 100 parts byweight asphalt. In these or other embodiments, the formation of theasphalt binder compositions of the present invention may employ lessthan 3 parts, in other embodiments less than 1 parts, in otherembodiments less than 0.5 parts, in other embodiments less than 0.25parts, in other embodiments less than 0.1 parts, and in otherembodiments less than 0.01 parts by weight curative (e.g., free sulfuror elemental sulfur) per 100 parts by weight asphalt binder.

In one or more embodiments, the phosphorus pentasulfide can be employedin the practice of the invention without the use of a polyphosphoricacid or derivative thereof. In certain embodiments, less than 1 part byweight, in other embodiments less than 0.1 parts by weight, in otherembodiments less than 0.05 parts by weight, and in other embodimentsless than 0.01 parts by weight polyphosphoric acid or a derivativethereof, per 100 parts by weight asphalt, is employed in practicing theinvention. In one or more embodiments, no polyphosphoric acid isemployed or added to the asphalt compositions. In one or moreembodiments, the asphalt compositions of this invention are devoid ofpolyphosphoric acid or the reaction products thereof with one or moreconstituents of the asphalt composition.

In one or more embodiments, the asphalt compositions of the presentinvention may include less than 1%, in other embodiments less than 0.5%,in other embodiments less than 0.1%, and in other embodiments less than0.05% by weight of an organophosphorous compound. In these or otherembodiments, the asphalt compositions of the present invention aresubstantially devoid of organophosphorous compounds, where substantiallydevoid refers to that amount or less of organophosphorous compound thatdoes not have an appreciable impact on the composition.Organophosphorous compounds include those disclosed in U.S. Pat. Nos.5,990,206 and 6,024,788, which are incorporated herein by reference.

In one or more embodiments, the modified asphalt binder compositions ofthis invention can be prepared by introducing asphalt binder with adesired amount of polymer (e.g., unsaturated polymer) and phosphoruspentasulfide at a desired temperature. In one embodiment, the polymerand phosphorus pentasulphide may be added to molten asphalt binder attemperatures greater than about 120° C., or in other embodiments fromabout 140° C. to about 210° C. In one or more embodiments, thephosphorus pentasulfide, polymer, and asphalt may be mixed or blendedafter or during introduction of the same. Mixing may then be continuedfor about 25 to about 400 minutes at a temperature of about 145° C. toabout 205° C. (or in other embodiments from about 160° C. to about 193°C.). In one or more embodiments, the mixture of the asphalt binder,polymer, and phosphorus pentasulfide may be sheared in order to dispersethe polymer quickly into the asphalt. Shearing may be accomplished, forexample, within a high shear mill such as that produced by Siefer. Inother embodiments, simple low shear mixing may be employed where time isless important. In one or more embodiments, the resulting modifiedasphalt binder of the composition is a homogeneous mixture, which is amixture where less than 1% by weight of polymer separates from theasphalt at 2° C. as determined by ASTM D-7173.

In one or more embodiments, the phosphorus pentasulfide mayadvantageously be added to the asphalt binder composition together with(i.e., simultaneously with) the polymer. In other words, the phosphoruspentasulfide need not be premixed into the asphalt binder prior toaddition of the polymer. Likewise, the polymer need not be premixed intothe asphalt binder composition prior to addition of the phosphoruspentasulfide.

In one or more embodiments, the phosphorus pentasulfide and polymer maybe added directly to the asphalt binder (e.g., molten asphalt binder)without preblending the phosphorus pentasulfide and unsaturated polymertogether. The phosphorus pentasulfide and polymer may be addedsimultaneously or sequentially to the asphalt binder. In one or moreembodiments, where the phosphorus pentasulfide and polymer are added tothe same binder composition, the phosphorus pentasulfide may be addedfirst, followed by the polymer. In other embodiments, the polymer may beadded to the asphalt binder first, followed by addition of thephosphorus pentasulfide.

In yet other embodiments, the phosphorus pentasulfide and unsaturatedpolymer may be separately introduced to and mixed with separate asphaltbinder compositions, and then the individual binder compositions may besubsequently introduced and blended. For example, phosphoruspentasulfide may be added to a first asphalt binder composition to forma first masterbatch binder composition. Likewise, polymer may be addedto a second asphalt binder composition to form a second masterbatchbinder composition. The first and second masterbatch compositions maythen be introduced and blended with each other to form a modifiedasphalt binder composition according to the present invention.

In one or more embodiments, the present invention provides a methodwhereby a concentrate of phosphorus pentasulfide and asphalt binder isintroduced and blended with a concentrate of polymer and asphalt binder.This method advantageously allows for the efficient transport and/orstorage of the phosphorus pentasulfide compositions and/or polymerasphalt binder compositions. In other words, it has been advantageouslydiscovered that by not introducing and combining the polymer, phosphoruspentasulfide, and asphalt binder, higher concentrations of thephosphorus pentasulfide and/or polymer within an asphalt bindercomposition can be achieved so long as the phosphorus pentasulfide andunsaturated polymer are introduced and mixed into separate binderconcentrates. Advantageously, the concentrates can be shipped to moreregional locations where they can be introduced and blended with eachother, and/or they can be advantageously diluted with additional asphaltbinder at the regional locations.

In one or more embodiments, the phosphorus pentasulfide-binderconcentrate can include greater than 0.5 parts by weight, in otherembodiments greater than 2.0 parts by weight, in other embodimentsgreater than 5.0 parts by weight, and in other embodiments greater than8.0 parts by weight phosphorus pentasulfide per 100 parts by weightasphalt. In these or other embodiments, the phosphoruspentasulfide-binder concentrate can include up to 10 parts by weight,and in other embodiments up to 12 parts by weight phosphoruspentasulfide per 100 parts by weight asphalt binder. Those skilled inthe art appreciate that the ability to process and handle the asphalt(e.g., pumpability per AASHTO T316) may dictate the upper levels ofphosphorus pentasulfide that can be added to an asphalt binder.

Similarly, the polymer-binder concentrate can include greater than 5parts by weight, in other embodiments greater than 10 parts by weight,in other embodiments greater than 15 parts by weight, and in otherembodiments greater than 18 parts by weight polymer per 100 parts byweight asphalt. In these or other embodiments, the polymer-binderconcentrate can include up to 20 parts by weight, in other embodimentsup to 25 parts by weight, and in other embodiments up to 30 parts byweight polymer per 100 parts by weight asphalt binder. Those skilled inthe art appreciate that the ability to process and handle the asphalt(e.g., pumpability per AASHTO T316) may dictate the upper levels ofpolymer that can be added to an asphalt binder. Other factors that mayimpact the upper limit of polymer concentration include polymermolecular weight, polymer macrostructure, and characteristics of theasphalt.

In one or more embodiments, the asphalt employed to prepare thephosphorus pentasulfide-binder concentrate may have differentcharacteristics than the asphalt employed to make the polymer-binderconcentrate. For example, in one embodiment, the asphalt employed toprepare the polymer-binder concentrate may be a softer asphalt than isused to prepare the phosphorus pentasulfide-binder concentrate. This maybe advantageous because greater loadings of polymer can be added tosofter asphalt, thereby providing the ability to transport and/or storemore polymer with less asphalt. Also, by preparing the phosphoruspentasulfide-binder concentrate and polymer-binder concentrate withdistinct asphalt, desirable properties can be achieved upon blending.For example, the phosphorus pentasulfide-binder concentrate can beprepared with a relatively hard asphalt, which when blended with thepolymer-binder concentrate made with a relatively soft asphalt, ahardness between the asphalt binders employed to make the concentratescan be achieved.

One particular embodiment of the method according to the presentinvention is shown in FIG. 1. A storage container of phosphoruspentasulfide 22, a storage container of asphalt binder 24, and a storagecontainer of unsaturated polymer 26 can be located at a modified asphaltbinder facility 12. A phosphorus pentasulfide-binder concentrate 28 canbe formed by introducing and blending phosphorus pentasulfide andasphalt binder. The step of introducing and blending can be achieved byadding particulate phosphorus pentasulfide to an asphalt bindercomposition maintained at a temperature of from about 120° C. to about205° C. Likewise, an unsaturated polymer-binder concentrate 30 can beprepared by introducing and mixing unsaturated polymer with asphaltbinder. The introduction and mixing of the unsaturated polymer andbinder can be achieved by adding pellets of unsaturated polymer to amolten asphalt binder composition maintained at a temperature of fromabout 120° C. to about 205° C. The respective asphalt binderconcentrates (i.e., concentrate 28 and concentrate 30) can then beshipped to a terminal 14. The shipping of the concentrates can occur byheated or insulated freight carrier. Advantageously, these concentratescan be shipped via insulated freight carrier to terminal 14 located upto and in excess of 1,000 miles from the modified asphalt binderfacility 12.

At terminal location 14, the phosphorus pentasulfide-binder concentrateand the unsaturated polymer-binder concentrate can be introduced andblended. This introduction and blending can occur at temperatures atabout 145° C. to about 170° C. Also, the concentrates, before or aftertheir introduction and blending, can be diluted with additional asphaltbinder, which can be stored at terminal 14 within container 32. Themodified binder 34, which is diluted to a desired level of phosphoruspentasulfide and/or unsaturated polymer as provided herein, may then betransported to a hot-mix plant 16. Transportation of this modifiedasphalt binder composition may occur within a heated or insulatedfreight container and can be shipped up to and in excess of 300 miles tohot-mix plant 16.

At hot-mix plant 16, the modified binder composition can be introducedand mixed with aggregate 36 to form paving composition 38. Methods forintroducing and mixing aggregate and modified binder composition areknown in the art and include batch mixing and continuous mixing. In oneor more embodiments, the aggregate and modified asphalt binder areintroduced and mixed by first preheating the modified asphalt binder toa temperature of about 120° C. to about 200° C. Once the pavingcomposition 38 has been prepared, the paving composition can betransported to a job site (e.g., road bed) where pavement can be paved.Transportation of the paving composition can occur within a heated orinsulated freight carrier.

The modified asphalt binder compositions prepared according to thepresent invention may be employed to prepare asphalt pavingcompositions. These paving compositions may include the modified asphaltbinder, aggregate, and other optional constituents that can be addedinto paving compositions as is known in the art. Conventional aggregatethat is used in the paving industry can be utilized in the practice ofthis embodiment. Aggregate may include rocks, stones, slags, crushedstone, gravel, sand, silica, or mixtures of one more thereof. Specificexamples of aggregates include marble, limestone, basalt, dolomite,sandstone, granite, quartzite, steel slag, and mixture of two or morethereof.

Aggregate typically has a wide distribution of particle sizes rangingfrom sub-micron particles (e.g., dust) to golf-ball sized masses aslarge as 63 mm in diameter. The best particle size distribution variesfrom application to application.

In addition to the aggregate and the modified asphalt binder, the pavingcompositions of the present invention may also include otherconstituents or ingredients that may be used in preparing asphalt pavingcompositions. These additional constituents or ingredients may includefibers, release agents, and fillers. Other examples include calciumhydroxide, sanders dust, cellulose fibers, propylene-based fibers, andmixtures of two or more thereof.

The asphalt paving compositions of the present invention can be preparedby using standard equipment and procedures. In one or more embodiments,the aggregate is mixed with the modified asphalt binder to attain anessentially homogeneous asphalt paving. For instance, the aggregate canbe mixed with the modified asphalt binder to produce asphalt pavingcomposition on a continuous basis in a standard mixer. In one or moreembodiments, practice of the present invention advantageously eliminatesthe need to treat the aggregate prior to formation of the asphaltconcrete.

When preparing an asphalt paving composition, generally from about 1weight percent to about 10 weight percent of the modified asphalt andfrom about 90 weight percent to about 99 weight percent aggregate (basedon the total weight of the asphalt paving composition) is mixed. Inother embodiments, the paving compositions include from about 2 to about8 weight percent of the modified asphalt.

The asphalt binder compositions, as well as the asphalt pavingcompositions, prepared according to the present invention demonstrateseveral advantageous properties. In one or more embodiments, thecompositions may advantageously be stored at elevated temperatureswithout deleteriously impacting the separation point of polymer andasphalt binder.

The asphalt paving compositions prepared according to the presentinvention are particularly advantageous for preparing pavements. Thesepavements may include, but are not limited to, roadway, airport runways,walkways, trails, golf cart paths, pond liner, landfill covers, andbridge decks. Also, the modified asphalt binder compositions of thepresent invention are advantageous for making other compositions besidesthe pavement compositions. For example, the modified asphaltcompositions may be useful in roofing applications.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Samples 1-7

Asphalt binder compositions were prepared by employing the followingmethod. To a quart can container was added 500 grams of asphalt binderpreheated to 163° C. The asphalt binder was obtained from BP (Whiting,Ind.) and had a PG rating of 64-22 per AASHTO M320. Using a quart canheater, the asphalt binder was heated to 190° C. and rotated on aSilverson high shear mixer at which time was added particulatephosphorus pentasulfide by direct addition of the particulate to theasphalt binder and pellets of unsaturated polymer by direct addition ofthe pellets to the asphalt binder. Shearing of the sample within thecontainer continued for 30 minutes. A lid was loosely placed on thecontainer, and the container was placed in an oven set at 163° C. for 18hours. Upon removal of the container from the oven, and removal of thelid, any skim layer present was removed. The sample was then stirred andpoured through a 20 mesh screen, and the screened material was used forpreparing test samples.

The amount of modifier (e.g. phosphorus pentasulfide and unsaturatedpolymer) added to each sample is set forth in Table I. A portion of eachsample was taken and prepared into various test specimens as requiredfor each standardized test employed. The test methods employedthroughout these Examples are provided in Table I.

The unsaturated polymer employed in this set of Samples was a radialpolymer that was characterized by about 16.5% vinyl, was 90%tetra-coupled, included about 30% block styrene, had a base peakmolecular weight (M_(p)) of about 53 kg/mole, and an M_(p) aftercoupling of about 228 kg/mole; this polymer was obtained under thetradename 161-B™ (LCY; China).

The amount of unsaturated polymer and phosphorus pentasulfide areprovided in Table I in parts by weight per 100 parts by weight asphalt(pha).

TABLE I Samples TEST Method 1 2 3 4 5 6 Modifier (parts per 100 asphalt)Unsaturated Polymer — 1.25 — 1.25 1.25 1.25 Phosphorus Pentasulfide — —0.5 — — 0.5 Polyphosphoric acid — — — — 0.5 — Sulfur — — — 0.1 — —Performance Analysis Original DSR Fail Temp. (° C.) AASHTO T315 65.569.0 70.6 71.6 72.5 78.7 RTFO DSR Fail Temp. (° C.) AASHTO T240/T31565.6 69.0 69.6 71.5 73.1 77.2 Phase Angle @ 76° C. AASHTO T315 89.0 87.487.5 79.4 85.1 69.7 Stiffness (MPa) AASHTO T313 210 228 205 195 210 166m-value AASHTO T313 0.329 0.304 0.326 0.332 0.309 0.345 PG Binder Grade(° C.) AASHTO M320 64-22 64-22 64-22 70-22 70-22 76-22 Estimated ActualGrade (° C.) n/a 65-24 69-22 69-24 71-25 72-22 77-26 PG Spread (° C.)n/a 89 91 93 96 94 103 Elastic Recovery @ 25° C. (%) AASHTO T301 24.044.0 34.0 72.5 48.5 87.5 Separation (° C.) ASTM D-7173 0.3 0.5 0.3 0.31.6 0.8 Softening Point (° C.) AASHTO T53 48.1 52.2 54.7 55.3 55.6 65.8

The PG estimated actual grade is a measure of the temperature spread ofthe asphalt binder performance temperature range. Adding the numberstogether gives the PG temperature spread. The larger the number, thegreater the performance temperature range over which the asphalt binderwill perform.

The asphalt binder of Sample 1, which is neat asphalt binder, performsover an 89° C. range. Sample 2, which includes saturated polymer, showsa 2° C. improvement from 89° C. to 91° C. Sample 3, which includesphosphorus pentasulfide, shows a small improvement in PG temperaturespread of 4° C. over the base asphalt. Sample 4, which includesunsaturated polymer and sulfur, shows a 7° C. improvement over neatbinder to 96° C. Sample 5, which includes unsaturated polymer andpolyphosphoric acid, shows a 5° C. improvement. Sample 6, which isindicative of the present invention, unexpectedly shows a 14° C.temperature improvement over the base asphalt to produce a PGtemperature spread of 103° C. Additionally, the elastic recovery (a.k.a.elongation recovery) of Sample 6, which is 87.5%, is exceptionally high,which suggests a highly elastic polymer asphalt binder that isconventionally achieved only with higher polymer loadings. The softeningpoint, as well as the PG high temperature estimate of 77° C., issuggestive of a technologically useful high temperature for the modifiedasphalt binder. Finally, the phase angle for Sample 6 was 69.7, which isan indication of a strong elastic structure formed in the asphaltbinder.

Samples 8-13

Additional modified asphalt compositions were prepared by employingmethods similar to those set forth in the preceding samples, but sampleswere prepared by employing saturated polymers for comparative samples(Samples 11, 12, and 13). Table II provides the amount of each modifieremployed in each sample as well as the results of performance analysisperformed on each sample.

The unsaturated polymer employed in Sample 8 was a radial polymer thatwas characterized by about 16.5% vinyl, was 90% tetra coupled, includedabout 30% block styrene, had a base peak molecular weight (M_(p)) ofabout 53 kg/mole, and an M_(p) after coupling of about 228 kg/mole; thispolymer was obtained under the tradename 161-B™ (LCY; China); thispolymer has been designated in the tables as the Radial Polymer.

The unsaturated polymer employed in Sample 9 was a linear, di-coupledpolymer that was characterized by about 13% vinyl, was 92% di-coupled,included about 30% block styrene, had a base peak molecular weight(M_(p)) of about 60 kg/mole, and an M_(p) after coupling of about 106kg/mole; this polymer was obtained under the tradename 6302™ (LCY;China); this polymer has been designated in the tables as the HighMolecular Weight Polymer.

The unsaturated polymer employed in Sample 10 was a linear, di-coupledpolymer that was characterized by about 13% vinyl, was 25% di-coupled,included about 30% block styrene, had a base peak molecular weight(M_(p)) of about 50 kg/mole, and an M_(p) after coupling of about 90kg/mole; this polymer was obtained under the tradename 6320™ (LCY;China); this polymer has been designated in the tables as the MediumMolecular Weight Polymer.

The saturated polymer employed in Sample 11 was a hydrogenatedstyrene-butadiene-styrene block copolymer (S-E/B—S) that was obtainedunder the tradename KRATON™ G1652.

The saturated polymer employed in Sample 12 was anethylene-propylene-diene rubber (EPDM) that was obtained under thetradename EP35 (JSR; Japan) and was characterized by a Tg of about −51°C., 0% crystallinity, a Mooney Viscosity (ML 1+4 @ 10° C.) of 91.6, anMn of about 72 kg/mol, an Mw of about 214 kg/mol, and MWD of about 2.94,an ethylene content of about 52% and a diene content of about 5.9%; itis noted that this polymer is not completely saturated.

The saturated polymer employed in Sample 13 was anethylene-vinyl-acetate polymer (EVA) that was obtained under thetradename ELVAX™ 460 (DuPont).

TABLE II Samples 7 8 9 10 11 12 13 Modifier (parts per 100 asphalt)Phosphorus Pentasulfide — 0.5 0.5 0.5 0.5 0.5 0.5 Unsaturated PolymerRadial Polymer — 1.5 — — — — — High Molecular Weight — — 1.5 — — — —Medium Molecular Weight — — — 1.5 — — — Saturated Polymer S-E/B-S — — —— 1.5 — — EPDM — — — — — 1.5 — EVA — — — — — — 1.5 Performance AnalysisOriginal DSR Fail Temp. (° C.) 65.5 80.6 77.8 75.1 74.1 73.3 74.0 RTFODSR Fail Temp. (° C.) 65.6 77.6 77.7 76.3 73.9 73.6 74.4 Phase Angle @76° C. 89.0 67.3 71.6 81.0 86.4 86.7 84.0 Elastic Recovery @ 25° C. (%)24.0 87.5 87.5 83.5 52.0 38.5 41.5 Separation (° C.) 0.3 0.5 0.3 0.3 1.10.3 0.4 Softening Point (° C.) 48.1 69.4 64.2 57.5 55.8 56.1 56.9

Sample 7 is Table II is the same neat asphalt binder employed in Sample1 of Table I. Samples 8-10 include unsaturated polymers, and the dataobtained from testing these modified asphalt binders show that theseunsaturated polymers yield binders that are more elastic (phase angleand elastic recovery) than expected for those polymer loadings. Thisunexpectedly indicates that the combination of unsaturated polymer andphosphorus pentasulfide produces a highly elastic asphalt binder.Additionally, RTFO DSR Fail Temperature (aging), the samples includingunsaturated polymer show improvements between 10.7° C. and 12° C. onhigh temperature performance over the neat asphalt binder. Additionally,Samples 8, 9, and 10 produced high elastic recoveries; indeed, each wasover 80%. On the other hand, the use of the saturated polymers (orpolymer having a low level of unsaturation) showed little elasticimprovement over the neat asphalt (there was some improvement in hightemperature stiffness 8.3° C.-8.8° C.). Overall, the data is Table IIsuggests a synergistic effect between the phosphorus pentasulfide,unsaturated polymer, and asphalt binder, which unexpectedly yields animproved elastic asphalt binder.

Samples 14-23

Several modified asphalt compositions were prepared by employing methodssimilar to those used in the above samples except that the weight ratiobetween the unsaturated polymer and phosphorus pentasulfide was variedthroughout the samples while keeping the polymer at 1.25 parts by weightper 100 parts by weight asphalt. The unsaturated polymer employed was aradial polymer that was characterized by about 16.5% vinyl, was 90%tetra coupled, included about 30% block styrene, had a base peakmolecular weight (M_(p)) of about 53 kg/mole, and an M_(p) aftercoupling of about 228 kg/mole; this polymer was obtained under thetradename 161-B™ (LCY; China). Table III provides the weight ratiobetween polymer and phosphorus pentasulfide, as well as the results oftesting on each Sample.

TABLE III Samples 14 15 16 17 18 19 20 21 22 23 Modifier (parts per 100asphalt) Polymer:Phosphorus 12.5:1 9:1 5:1 3.1:1 2.5:1 2.1:1 1.8:1 1.6:11:1 1:2 Pentasulfide Performance Analysis Original DSR Fail Temp. (° C.)70.6 72.7 73.0 76.7 78.7 81.0 83.1 83.5 79.8 86.5 RTFO DSR Fail Temp. (°C.) 71.2 71.9 72.3 74.8 77.2 78.8 80.4 80.8 77.2 84.3 Phase Angle @ 76°C. 81.8 78.4 75.3 71.6 69.7 66.5 65.6 65.9 81.2 76.6 Elastic Recovery @25° C. (%) 69.0 72.5 78.0 83.5 87.5 89.0 88.0 88.0 38.5 41.5 SofteningPoint (° C.) 53.9 56.7 57.5 61.9 65.8 69.7 72.5 72.2 60.8 67.8Separation (° C.) 0.3 0.3 0.5 0.5 0.8 0.5 0.5 0.5 0.8 0.3

The data in Table III shows an unexpected effect of changing the ratioof polymer to phosphorus pentasulfide. As the ratio falls, the elasticrecovery of the modified binder increases, peaking around 1.8:1. As theratio continued to decrease, the elastic recovery then started todecrease. Additionally, the phase angle decreases steadily to the 1.8:1ratio then increases below the ratio.

Samples 24-33

In a manner similar to Samples 14-23, additional modified asphaltcompositions were prepared and the weight ratio between the unsaturatedpolymer and phosphorus pentasulfide was varied while keeping the polymerat 1.25 parts by weight per 100 parts by weight asphalt. These samplesdiffer from Samples 14-23 based upon the unsaturated polymer employed,which was a linear, di-coupled polymer that was characterized by about13% vinyl, was 25% di-coupled, included about 30% block styrene, had abase peak molecular weight (M_(p)) of about 50 kg/mole, and an M_(p)after coupling of about 90 kg/mole; this polymer was obtained under thetradename 6320™ (LCY; China).

Table IV provides the weight ratio between polymer and phosphoruspentasulfide, as well as the results of testing on each Sample.

TABLE IV Samples 24 25 26 27 28 29 30 31 32 33 Modifier (parts per 100asphalt) Polymer:Phosphorus 12-5:1 9:1 5:1 3.1:1 2.5:1 2.1:1 1.8:1 1.6:11:1 1:2 Pentasulfide Performance Analysis Original DSR Fail Temp. (° C.)69.4 69.9 70.9 73.3 74.7 77.2 78.4 80.2 81.7 87.2 RTFO DSR Fail Temp. (°C.) 69.4 69.4 70.7 73.0 73.2 76.1 78.2 78.8 80.3 85.7 Phase Angle at 76°C. 86.3 86.0 85.5 83.7 81.7 78.0 75.5 73.1 76.7 73.8 Elastic Recovery @25° C. (%) 64.0 66.5 71.5 74.5 81.5 83.5 84.5 83.0 45.0 40.5 SofteningPoint ° C. 52.5 53.6 55.0 56.7 57.2 60.8 61.7 62.8 64.4 68.9 Separation(° C.) 0.5 0.3 0.3 0.3 0.5 0.3 0.3 0.3 0.3 0.5

As with the data in Table III, the data in Table IV shows that as theratio was lowered, the elastic recovery increased, peaking at 1.8:1.Similarly, the elastic recovery started to decrease unexpectedly belowthis ratio. Phase angle followed a pattern of decreasing phase anglewith decreasing ratios until 1.6:1, then increased.

Samples 34-45

Additional modified asphalt compositions were prepared by employingmethods similar to those used in the above samples except that theefficacy of phosphorus pentasulfide was compared to other compounds. Thenature of the sundry compounds is provided in Table VI together with theresults of testing on each Sample.

The unsaturated polymer employed was a radial polymer that wascharacterized by about 16.5% vinyl, was 90% tetra coupled, includedabout 30% block styrene, had a base peak molecular weight (M_(p)) ofabout 53 kg/mole, and an M_(p) after coupling of about 228 kg/mole; thispolymer was obtained under the tradename 161-B™ (LCY; China).

TABLE V Samples 34 35 36 37 38 39 40 41 42 43 44 45 Modifier (parts per100 asphalt) Polymer 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5Additive P₂S₅ 0.5 — — — — — — — — — — — ZnS — 0.5 — — — — — — — — — —Al₂S₃ — — 0.5 — — — — — — — — — FeS — — — 0.5 — — — — — — — — Sb₂S₃ — —— — 0.5 — — — — — — — MoS₂ — — — — — 0.5 — — — — — — Sb₂S₅ — — — — — —0.5 — — — — — SeS₂ — — — — — — — 0.5 — — — — P₂O₅ — — — — — — — — 0.5 —— — H₃PO₄ — — — — — — — — — 0.5 — — PCl₃ — — — — — — — — — — 0.5 — POCl₃— — — — — — — — — — — 0.5 Performance Analysis RTFO DSR Fail Temp. (°C.) 78.1 70.6 70.6 70.9 70.6 69.0 71.6 71.8 73.6 74.1 70.6 70.5 ElasticRecovery @ 25° C. (%) 87.5 49.0 65.0 49.5 50.5 45.0 67.0 44.0 56.0 62.051.0 51.0 Softening Point ° C. 63.3 51.9 53.3 51.9 52.2 51.7 53.3 51.156.9 55.6 55.8 56.4

The data in Table V shows in comparing many other compounds tophosphorus pentasulfide, an unexpected outcome is that phosphoruspentasulfide consistently has the highest stiffness as measured by AfterRTFOT DSR failure temperature. Additionally phosphorus pentasulfideproduced a significantly higher elastic recovery. Finally, phosphoruspentasulfide produced the highest overall softening point.

Samples 46-51

Additional samples were prepared using techniques similar to thoseprovided above. In this series of samples, the amount of polymer loadingper 100 parts by weight asphalt was varied. The amount of polymer ineach sample is provided in Table VI together with the results of testingthat was performed.

In Samples 46 and 49, the unsaturated polymer was a radial polymer thatwas characterized by about 16.5% vinyl, was 90% tetra coupled, includedabout 30% block styrene, had a base peak molecular weight (M_(p)) ofabout 53 kg/mole, and an M_(p) after coupling of about 228 kg/mole; thispolymer was obtained under the tradename 161-B™ (LCY; China), and isdesignated Radial Polymer.

In Samples 47 and 50, the unsaturated polymer was a linear, di-coupledpolymer that was characterized by about 13% vinyl, was 92% di-coupled,included about 30% block styrene, had a base peak molecular weight(M_(p)) of about 60 kg/mole, and an M_(p) after coupling of about 106kg/mole; this polymer was obtained under the tradename 6302™ (LCY;China); this polymer has been designated in the tables as the HighMolecular Weight Polymer.

In Samples 48 and 51, the unsaturated polymer was a linear, di-coupledpolymer that was characterized by about 13% vinyl, was 25% di-coupled,included about 30% block styrene, had a base peak molecular weight(M_(p)) of about 50 kg/mole, and an M_(p) after coupling of about 90kg/mole; this polymer was obtained under the tradename 6320™ (LCY;China); this polymer has been designated in the tables as the MediumMolecular Weight Polymer.

TABLE VI Samples 46 47 48 49 50 51 Modifier (parts per 100 asphalt)Polymer Radial Polymer 4 — — 1.5 — — High Molecular — 4 — — 1.5 — WeightPolymer Medium Molecular — — 4 — — 1.5 Weight Polymer PhosphorusPentasulfide — — — 0.5 0.5 0.5 Sulfur 0.1 0.1 0.1 — — — PerformanceAnalysis Original DSR Fail 81.6 80.7 76.4 80.6 77.8 75.1 Temp. (° C.)RTFO DSR Fail Temp. (° C.) 77.2 76.6 74.0 77.6 77.7 76.3 Phase Angle @76° C. 64.7 66.3 72.2 67.3 71.6 81.0 Elastic Recovery @ 91.0 88.5 84.587.5 87.5 83.5 25° C. (%)

Table VI shows that 4 parts of polymer per 100 parts by weight asphalttogether with sulfur as an accelerator gave results very similar to theuse of 1.5 parts by weight polymer per 100 parts by weight asphalt usingphosphorus pentasulfide. Significantly, the results achieved between therelated samples were substantially similar in each of the performancecriteria. This is advantageous inasmuch as the present invention allowsfor comparable performance at much lower polymer loading.

Without wishing to be bound by any particular theory or reactionmechanism, it is believed that the modified asphalt binder compositionsof one or more embodiments of the present invention may include reactivecrosslinks between components of the asphalt binder and the unsaturatedpolymer. It is speculated that these reactive crosslinks may includephosphorus and sulfur atoms that bridge between hydrocarbon-basedconstituents in the asphalt binder, such as asphaltenes, and/or thepolymer chains. In one or more embodiments, the reactive crosslinks mayinclude phosphorus-sulfur groups attached to carbon atoms of the asphaltbinder constituents and/or polymer. In these or other embodiments, thecrosslinks may include phosphorus-sulfur-phosphorus groups attached tocarbon atoms of the asphalt binder and/or polymer. For example, thereactive crosslink may include a bridge represented bycarbon-phosphorus-sulfur-phosphorus-carbon, where the carbon atoms arepart of respective constituents within the asphalt binder and/orpolymer. It is believed that the phosphorus-sulfur bonds are reactive,which means that they are susceptible to attack by other reactivespecies such as nucleophiles. Inasmuch as nucleophiles are readilypresent in asphalt binders, it is believed that a dynamic situation mayexist within the modified asphalt binders of the present inventionwhereby the reactive crosslink can be attacked and form phosphorus andsulfur links to various constituents within the asphalt binder orperhaps even the unsaturated polymer. It is believed that thephosphorus-sulfur crosslinks can be achieved by compounds that canprovide both a source of sulfur and a source of phosphorus in aparticular molecular arrangement. One such compound that can providethese sources, and which has is been found to unexpectedly provideunique modified asphalt binder compositions together with polymer, isphosphorus pentasulfide.

In one or more embodiments of the present invention, an advantage thathas been unexpectedly achieved is the ability to achieve technologicallyuseful and modified asphalt binder compositions at relatively lowpolymer loading based upon the weight of the asphalt binder. Forexample, in one or more embodiments, modified asphalt binderscompositions prepared with phosphorus pentasulfide and less than 2.5parts by weight, in other embodiments less than 2.0 parts by weight, inother embodiments less than 1.8 parts by weight, and in otherembodiments less than 1.5 parts by weight polymer demonstrate a phaseangle at 76° C., as determined according to AASHTO T315, of less than80°, in other embodiments less than 77°, in other embodiments less than75°, in other embodiments less than 72°, and in other embodiments lessthan 70°. Similarly, in one or more embodiments, modified asphaltbinders compositions prepared with phosphorus pentasulfide and less than2.5 parts by weight, in other embodiments less than 2.0 parts by weight,in other embodiments less than 1.8 parts by weight, and in otherembodiments less than 1.5 parts by weight polymer demonstrate anelongation recovery (a.k.a. elastic recovery) at 25° C., as determinedaccording to AASHTO T301, of greater than 75%, in other embodimentsgreater than 77%, in other embodiments greater than 80%, in otherembodiments greater than 83%, and in other embodiments greater than 85%.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A modified asphalt binder composition prepared by: combining asphaltbinder, phosphorus pentasulfide, and less than 2.5 parts by weightunsaturated polymer, per 100 parts by weight asphalt binder, to therebyproduce a modified asphalt binder composition characterized by anelongation recovery at 25° C., as determined according to AASHTO T301,of greater than 75%.
 2. The composition of claim 1, where the bindercomposition is prepared by combining from about 0.05 to about 5 parts byweight phosphorus pentasulfide per 100 parts by weight asphalt binder.3. The composition of claim 1, where the binder composition ischaracterized by an elongation recovery at 25° C., as determinedaccording to AASHTO T301, of greater than 77%.
 4. The composition ofclaim 1, where the binder composition is characterized by an elongationrecovery at 25° C., as determined according to AASHTO T301, of greaterthan 80%.
 5. The composition of claim 1, where the binder composition isprepared by combining less than 2.0 parts by weight unsaturated polymerper 100 parts by weight asphalt binder.
 6. The composition of claim 1,where the binder composition is prepared by combining less than 1.8parts by weight unsaturated polymer per 100 parts by weight asphaltbinder.
 7. The process of claim 1, where the polymer includes a blockcopolymer including at least one block including units deriving from thepolymerization of conjugated diene monomer, and at least one blockincluding units deriving from the polymerization of vinyl aromaticmonomer.
 8. An asphalt paving composition prepared by combining themodified asphalt binder composition of claim 1 with aggregate.
 9. A roadsurface prepared from the asphalt paving composition of claim
 3. 10. Theprocess of claim 1, where the polymer and phosphorus pentasulfide areadded simultaneously to the asphalt binder.
 11. The process of claim 1,where the polymer and phosphorus pentasulfide are added sequentially tothe molten asphalt binder.
 12. The process of claim 1, where the weightratio of polymer to phosphorus pentasulfide is at least 0.7:1 and lessthan 7:1.
 13. The process of claim 7, where the weight ratio of polymerto phosphorus pentasulfide at least 1:1 and less than 6:1.
 14. Theprocess of claim 8, where the weight ratio of polymer to phosphoruspentasulfide is at least 1.3:1 and less than 5:1.
 15. The process ofclaim 1, where the polymer is an unsaturated polymer including at least5 non-conjugated double bonds per 100 carbon atoms in the polymer. 16.The process of claim 1, where the phosphorus pentasulfide is introducedto the asphalt binder by direct addition of the phosphorus pentasulfideto the asphalt.
 17. A modified asphalt binder composition prepared by:combining asphalt binder, phosphorus pentasulfide, and less than 2.5parts by weight unsaturated polymer, per 100 parts by weight asphaltbinder, to thereby produce a modified asphalt binder compositioncharacterized by a phase angle at 76° C., as determined according toAASHTO T315, of less than 80°.
 18. The composition of claim 17, wherethe modified asphalt binder composition characterized by a phase angleat 76° C., as determined according to AASHTO T315, of less than 77°. 19.The composition of claim 17, where the modified asphalt bindercomposition characterized by a phase angle at 76° C., as determinedaccording to AASHTO T315, of less than 75°.